This invention relates to a gas or air bearing comprising at least two bearing parts movable with respect to each other, gas injection means being present between the two bearing parts working faces facing each other for injecting a gas in order to be able to maintain a gas gap between the bearing parts.
These air bearings comprising two bearing parts rotatable with respect to each other and made of ceramic material, 10 glass and/or metal are generally known. Such air bearings offer the great advantage that they operate without friction even in the case of large and heavy structures, without any lubricant being used.
To obtain a very thin air gap between the bearing parts, the latter may be provided with air conduction grooves through which ambient air is fed between the two working faces of the rotatable bearing parts to form a very thin air gap. The use of a very small air gap is necessary in order to obtain the desired stability of the air bearing.
A drawback of said known air bearings is that they are expensive because of the use of expensive bearing parts of the materials mentioned.
It has emerged, however, that although replacement of the ceramic material by, for example, natural stone, in particular granite, leads to considerable savings through the use of a much cheaper starting material for the bearing parts, such a large number of pores occurs in the surfaces of the working faces of the bearing parts which are formed in manufacturing the bearing parts from large blocks of natural stone that although the surface is flat, it is not impermeable to gases, as a result of which the gases leak away and an air gap of the desired constant thickness cannot be maintained. This results in the production of undesirable vibrations in the bearing.
The above drawback of the gases leaking away and the production of vibrations is made yet more severe by the fact that the porosity in the surfaces of the working faces of the bearing parts is not often the same everywhere, but varies from point to point.